Phase control circuits are used in a variety of applications such as in transceivers to synthesize clock signals or to recover data from a data stream in a clock and data recovery (CDR) application. They typically use a voltage controlled oscillator (VCO) or a phase interpolator (PI) to generate an output signal with a controllable phase angle (or phase).
PI type phase control circuits may be digital or analog. Digital PI-based circuits typically control a phase interpolator with one or more digital words having a fixed number of possible values. They can perform well but may be limited due, for example, to their limited resolution, which can make it difficult to use them in higher frequency applications. On the other hand, analog PI controllers have better phase control resolution but may have other drawbacks such as when a frequency offset exists between PI core reference clocks and the incoming frequency signal to be tracked, there can be a perpetual output phase offset, i.e., a non-zero static phase error. Accordingly, improved phase control solutions are desired.